Among women who are aware of their pregnancy, the rate of spontaneous abortion—or miscarriage—is 15 to 20% and typically occurs during the first 7 weeks. Despite these troubling statistics, the cause of recurrent spontaneous abortion remains elusive. Now, a new study by Tavakoli et al. on the effects of vitamin D during early pregnancy may shed light on a new approach to the evaluation and management of women who suffer repeated miscarriages.

Researchers have identified several mechanisms behind spontaneous abortions, such as anatomical uterine abnormalities or the presence of specific maternal antibodies. However, women who do not display these conditions also struggle with recurrent and unexplained miscarriage, leaving this subset of infertility patients with few explanations and options. Attention has recently turned to the endometrial lining as a cause, specifically the interface between the early embryo and the cells programmed to assist in implantation. The authors examined the role that 1,25(OH)2 vitamin D3 plays in the production of proinflammatory cytokines that can interfere with implantation by studying endometrial cells from women with unexplained miscarriage and matched controls. Results showed that an unfractionated endometrial cells as well as isolated endometrial stromal cells that had been exposed to 1,25(OH)2 vitamin D3 produced statistically significant lower levels of the proinflammatory cytokines interleukin-10 (IL-10) and IL-6. In addition, both populations of uterine-lining cells, when exposed to vitamin D3, demonstrated a decrease in the interferon-γ:IL-10 ratio that can spur miscarriage. The authors suggest that these findings may lead to the development of a therapeutic approach for patients who are prone to immune-mediated pregnancy loss. Given the growing incidence of unexplained infertility—which is now 10 to 12% of the population—prospective parents are expecting new approaches to the prevention of miscarriages.